Two families of prefixes
A byte is the common starting point, but the prefixes take two different paths. In the decimal SI family, 1 kB is 1,000 bytes, 1 MB is 1,000,000 bytes, 1 GB is 1,000,000,000 bytes, and 1 TB is 1,000,000,000,000 bytes. These are powers of ten. The letters are case sensitive: B denotes bytes, while b denotes bits.
The binary family uses powers of 1,024 and gives them distinct names. One KiB is 1,024 bytes; one MiB is 1,048,576 bytes; one GiB is 1,073,741,824 bytes; one TiB is 1,099,511,627,776 bytes. IEC uses these binary names to remove ambiguity. An unqualified “MB” should therefore not silently stand for 1,048,576 bytes.
A worked comparison
Suppose a file contains exactly 1,000,000,000 bytes. Its decimal size is 1 GB. Divide the byte count by 1,073,741,824 to obtain about 0.9313 GiB. Nothing was removed: both expressions describe precisely the same amount of data. Similarly, 1,000 MB divided by 1.048576 gives about 953.674 MiB.
The apparent gap grows with larger prefixes because the ratios compound. A nominal 1 TB corresponds to about 0.9095 TiB before any formatting or file-system effects. To compare two reports, first convert both to bytes or to the same named unit. Then round only the final display value; an early rounded figure can hide a small but real difference.
- 1,000,000,000 bytes
- 1 GB in decimal units
- about 0.9313 GiB in binary units
Where the distinction matters
This distinction helps when checking a disk label against a system display, planning a backup, interpreting a cloud storage limit, or comparing the reported size of a downloaded file. A transfer rate adds another trap: Mb/s is megabits per second, whereas MB/s is megabytes per second. There are eight bits in a byte, so the letter case changes the quantity substantially.
If an application reports a smaller number than the package, inspect its unit label and documentation before concluding that capacity is missing. File systems may also reserve space for metadata, and manufacturers or operating systems can round displayed totals differently. Those are separate effects; converting GB to GiB explains only the decimal-versus-binary part.
A practical checking method
Start with the quantity and the exact label supplied by the source. If you know the byte count, divide by 1,000,000 for MB or 1,048,576 for MiB. For GB and GiB use 1,000,000,000 and 1,073,741,824 respectively. MultiVerto can handle the direct MB-to-MiB, GB-to-GiB and TB-to-TiB steps when you need a quick comparison.
Keep the original value alongside the converted value in a report, for example “1 GB (about 0.931 GiB)”. This makes the chosen convention visible to the next reader. For storage procurement or capacity alerts, use the unit specified in the contract or software threshold rather than an informal abbreviation. A conversion changes the number and unit; it does not increase usable space.
Read the full context of a storage figure
A device’s advertised capacity, a partition’s size, free space, and the sum of stored file sizes are four different quantities. Before comparing them, identify which one the screen measures. A formatted volume can have a different usable capacity from its physical device, and free space will also reflect files already present. No unit conversion can reconcile those separate accounting choices by itself.
For a repeatable check, record the source number, its unit, the exact byte count if available, and the date or state of the device. Convert the byte count in both systems and compare like with like. If the remaining discrepancy matters, inspect partition layout, reserved space and file-system reporting. The conversion is the first diagnostic step, not an explanation for every capacity difference.